In a WTA rife with comebacks, injuries, and opportunists, the middle weekend often offers tennis as scintillating as the tournament’s climax. That theme may continue with a fourth-round rematch of the 2011 Australian Open final, which will feature two of the three most impressive performers in this half of the draw. Dropping just seven games in her last five sets, Clijsters has played herself into the fortnight and has survived the early meltdowns that have ambushed her at occasional Slams during her second career. In a commanding victory over Hantuchova, who had troubled her in Brisbane this month, the defending champion retrieved and redirected balls with her familiar aplomb while showing no sign of her recent hip injury. When healthy, Clijsters can transition from defense to offense more effectively than any woman in the WTA, except perhaps her opponent on Sunday. Two victories from a third straight semifinal in Melbourne, Li has looked crisp as she once again has extended her momentum from a fine week in Sydney. The Roland Garros champion owns the single most explosive weapon in this match with her forehand, although her two-hander has not failed to impress. Overlooked amidst their excellent groundstrokes and movement are the serves of both women, which have functioned effectively this week. Both Clijsters and Li possess very complete games and clean technique but can misfire for extended stretches, either through the presence of nerves or the absence of focus. Unless they find their rhythms at the same time, a rollercoaster encounter could result, decided by who can finish points more effectively once they seize the initiative.

We preview each of the other singles matches as the second week begins.

Azarenka vs. Benesova: Perhaps catalyzed by her Brisbane upset of Stosur, the least famous of the three Czech lefties extended her success here by comfortably defeating Peng. Benesova exploited an open section of the draw, vacated by Schiavone, by swinging her hook serve and forehand to jerk less powerful opponents around the court. But now the competition jolts upward abruptly against the third seed, who has looked one of the leading three or four title contenders here despite a wobble in her previous match. As match point after match point slipped away against Barthel, Azarenka’s carefully managed nerves started to fray visibly until she unleashed a concluding burst of petulance mixed with relief. Maintaining outstanding depth on her groundstrokes throughout the first week, she should succeed against Benesova simply by staying steady in both playing style and emotions. Perhaps the most balanced player of her generation, Azarenka treads a middle path between the dogged counterpunching of Wozniacki and the fearless, sometimes reckless assaults of Kvitova. Her serve remains the weakest component of her game, but she has protected it well here and has not yet encountered an elite returner. Against Benesova, her backhand down the line should prove especially lethal as Azarenka aims to reach her second Melbourne quarterfinal with minimal difficulty.

Lopez vs. Nadal: As the tournament began, Nadal generated news related to the ATP schedule, his opinion of Federer, and another injury to his knee. To the relief of his fans, he generated little news related to his tennis during an uneventful first week of straight-sets victories. Experimenting with a heavier racket, his serve has looked clearly more formidable although still not at its level when he won the US Open. Outside an occasional sloppy service game against Haas and Lacko, Nadal has provided his critics with scant ground for complaint so far. With the exception of a Queens Club upset, he has suffocated Lopez throughout their careers by relying upon his far superior baseline consistency to erode his fellow lefty. The older Spaniard impressed by conquering Isner in a five-setter during which her broke the American’s towering serve six times while losing his own serve only once. But he struggled with double faults throughout that match, committing four during one crucial game that exposed his nerves. Always high in winners and high in unforced errors, Lopez must record an outstanding first-serve percentage to threaten his compatriot on a sticky surface that blunts serves and rewards baseliners. Not until the semifinal, perhaps, will Nadal find an adversary worthy of his steel.

Tomic vs. Federer: In all three of his first-week matches, the home hope lost the first set as Melbourne heart rates accelerated. Buoyed by the fervent Rod Laver crowds, Tomic demonstrated stamina remarkable for a teenager as he outlasted both Verdasco and Dolgopolov in five sets. All the same, he cannot afford to allow Federer an early lead as he settles into the match, for the Swiss legend has proven himself an outstanding front-runner against heavy underdogs throughout his career. After playing 14 sets in three matches and running for four miles on Friday night, Tomic will need to recover quickly for a match that will require crisp footwork, keen instincts, and a clear mind. When he faced Federer in a Davis Cup playoff last fall, the teenager won a set and competed valiantly in the others. The difference in that collision, the contrast between their serves could play a crucial role again as the 16-time major champion holds much more comfortably, while Tomic expends more effort on each service game. Severely tested for nearly two full sets by Karlovic’s serve, Federer should feel less inconvenienced by the veering slices and spins of the Australian’s distinctive style. As his career wanes, muscular ball-bruisers like Soderling, Tsonga, and Berdych have unsettled him, but the crafty artists of the court have enjoyed little more success against him on hard courts than they ever have.

Wozniacki vs. Jankovic: After losing the first four meetings to her fellow counterpuncher and stylistic ancestor, the world #1 defeated Jankovic three times last year in a striking momentum shift. Many are the similarities between these women, who rely upon their movement more than their serving and project greater power from their backhands than their forehands. Outside a shaky second set in the second round, Wozniacki has acquitted herself creditably throughout the first week, showing few signs of crumbling under the pressure of her ranking. In the Dane’s position three Australian Opens ago, Jankovic succumbed in the fourth round and would not capture the top spot again. With the opportunity to strip it from her opponent, she may bring more motivation than she has shown for much of her steady decline. Overwhelming a trio of young challengers, such as the promising Christina McHale, Jankovic displayed few traces of her vintage self but did maintain her focus consistently as she waited for the raw teenagers across the net to falter. The Serb saved break point after break point against McHale in a match that looked extremely tight early before developing into a rout. Considering their stylistic parallels, this encounter of current and former #1s should hinge mostly upon execution. Jankovic would seem to hold the edge in power and experience, while Wozniacki enjoys the advantage in mobility, consistency, and (arguably) composure, but each could surpass the other in any of these dimensions on any given day. Expect a lung-burning series of rallies along the baseline as both women aim to win points than invite the opponent to lose them.

Goerges vs. Radwanska: One of two Germans to reach the second week at the Australian Open, Goerges enjoyed a promising first half to 2011 before fading dramatically—even evaporating—in the second half. When she retired against Jankovic in Sydney, one harbored few hopes for her Melbourne campaign despite a resilient performance in a three-set loss to Sharapova last year. Again showcasing her bold brand of tennis on these courts, she has recorded the strongest Slam effort of her still budding career and should not underestimate her chances to progress further. Never more than a quarterfinalist at majors, Radwanska has demonstrated her ability to score a key upset here or there but has not produced a deep run, regularly undone by a player who overpowers her from the baseline and from the service notch. During a stirring Asian fall, however, the Pole suggested that she might have enhanced her readiness to take risks, even if her puny serve may have no remedy. She nearly stumbled against Mattek-Sands in her opening match but used her survival instincts to escape an opponent who cracked 80 winners. Clearly superior to Radwanska on serve, Goerges will need to earn plentiful free points from that shot if she seeks to subdue her exceptionally nuanced, clever, and tenacious foe. Once rallies begin, the eighth seed will hope to expose the German’s deficiencies in mobility and point construction, perhaps dragging her forwards at inconvenient moments. To become a truly premier contender, Radwanska must overcome the second tier of ball-bruisers like Goerges more regularly.

Berdych vs. Almagro: The match most likely to feature a fifth set, this meeting of the world #7 and world #10 seems academic in a sense because the winner will have only a negligible chance of upsetting Nadal. A quarterfinal appearance still would represent a significant accomplishment for Almagro, whose game aligns just as well with hard courts as with clay. But he has not excelled at the most prestigious events, managing just two Roland Garros quarterfinal amidst a host of first-week exits to far less talented opponents. In stark contrast to the functional two-handed backhand of Berdych, Almagro’s elegant one-hander exemplifies his elongated swings, which can cost him time on faster surface. These medium-speed hard courts should allow him to set up his elaborate swings without slowing the Czech’s serve too significantly. Winning all three of his tiebreaks this fortnight, Berdych has relied upon his most formidable shot to set up his inside-out and inside-in forehands. To reach his second straight Australian Open quarterfinal, he should keep Almagro pinned well behind the baseline, where he will struggle to penetrate the court and may attempt low-percentage shots from frustrated impatience. Since they lack the ability to transition smoothly from defense to offense, the player who can assert himself early in the point usually will emerge victorious. In their only previous hard-court meeting, at Cincinnati last year, Berdych delivered the terminal blow earlier and more often, winning with ease.

Kohlschreiber vs. Del Potro: In all four of their previous meetings, the US Open champion has emerged triumphant, but their two 2011 clashes hint at intrigue ahead. Since an opening five-setter, Kohlschreiber has played only four and a half sets in two rounds, so he should bring plenty of energy to track down the Argentine’s lasers. Following an indifferent beginning to the tournament, Del Potro has looked more authoritative with each match and almost each set that he has seized. As he completed his demolition of a helpless Yen-Hsun Lu on Friday night, his forehands rocketed through the court with an ominous explosiveness. Nevertheless, Kohlschreiber can trade baseline bombs with the Argentine on both groundstroke wings, relishing the opportunity to redirect balls down the line. The product of a particularly fluid motion, his serve sets up points almost as well as does Del Potro’s mightier delivery. Content to decide points from the baseline, the Tower of Tandil rarely ventures towards the net, whereas the German will test his opponent’s passing shots by approaching opportunistically. That strategy could help Kohlschreiber destabilize Del Potro’s timing, uneven since his wrist surgery. In a best-of-five format, though, the Argentine’s heavier weight of shot and suffocating court coverage should frustrate a thrilling shot-maker who plays with much less margin for error.